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MAINTENANCE
Opportunities to reduce costs
By Peter Wolff of Armstrong
W
hen faced with beneficial improvements? were not throttled back on the impeller trimmed to
replacing an If you can answer ‘yes’ to any main commissioning set. So the exact duty,
ageing pump, of the following then there are they’re wasting power over a minimising
engineers often financial and energy efficiency flow/head point in excess of the waste
install a like-for- benefits to be had. real need.
like replacement, even though • Are any of the pumps belt- The belt and pulley drive
this can mean missing out on driven? absorbs power, reducing pump
more energy efficient • Are they started by direct on operating efficiency and
technology. Concerns often line or Star Delta starters? wasting money. If the pulley
relate to the cost and disruption • Are cold water booster sets drive is not in A1 alignment and
of selecting alternative fitted with horizontal tension, it will become noisy,
equipment. The scale of these pumps? potentially leading to issues
problems is, however, • Are commissioning valves with the building occupants.
frequently over-estimated. on the main headers part And when it’s in this condition,
The replacement or closed? the drive absorbs even more
refurbishment solution can be • Is the heating or chilled power, increasing the relative
chosen according to the budget water system fitted with cost of ownership.
available. With today’s cost three port valves and by- completely and
analysis technology it’s very pass circuits? Option 1 – the solution installing a new high
easy to calculate the payback Each of the following options Replace the belt-driven pump efficiency unit benefiting from
period, and it then becomes a assumes that the equipment to with a close coupled relative of sensorless variable speed
simple trade-off, to balance the be replaced is a belt driven the installed pump, using the e n e r g y . drives.
outlay with the potential cost pump with duty of 20l/s at existing pump casing and This would
and carbon reductions. 160kPa. The cost savings are pipework. The impeller in the deliver a 17% saving in Option 2 – Option 3 – the solution
Many improvements can be calculated on the basis of an replacement pump is trimmed absorbed power. installation There are a wide range of low
made leaving the plant room electricity cost of 10p/kWH and to the exact duty requirements, No pipe changes are needed. carbon opportunities, including
pipework untouched. Just keep 8000 hours/year running. allowing the commissioning set Option 2 – the Keep the existing body casing the latest control technology,
the existing body casing with to be opened-up, reducing opportunity with the inlet-outlet connections which balances demand across
inlet/outlet connections in Option 1 – the power absorbed and saving Most old pumps are running at in place but remove the rest of the system to achieve the
place, and remove the rest of opportunity money. There are no energy- 100% design flow all the time the pump set. Replace it with a optimal wire to water efficiency
the pump set. Then replace it Most of the old belt-driven wasting belt drive losses. The with the heating or cooling close coupled pump with based on the most efficient use
with a new close coupled pump, pumps installed have been motor is also sized to the actual controls by-passing fluid integrated frequency inverter, of each component. Pipeline
supplied without its body oversized, to allow for possible working duty, not over-sized, so through a parallel circuit, using converting from three port mounted vertical in-line pumps
casing. This rotating assembly extra system resistance or it is more energy efficient and a three port control valve, when control valves to two port can be considered, which
can be fitted with an integrated future duty increases. The saves money. it is not needed. operation. The by-passes remove the need for inertia
frequency inverter if required to pump end operating speed was This replacement option also Variable speed drive pumps become redundant. With bases, and there are numerous
bring the benefits of variable only ever a near fit to the actual brings quieter operation and offer an excellent replacement, sensorless software built into packaged/offsite manufactured
speed drive operation. duty because the limited reduced maintenance but it is often thought that this the drive, the motor will options, such as Armstrong’s
number of pulley sizes available requirements. Belt-driven will be complex and involve automatically sense when the Pumpbox.
Low-hanging fruit reduced the number of speeds pumps need their belt tension large-scale work. This is not the two port valves are opening or
So where do you look first for available for selection. Most and pulley alignment checked case. The move to variable closing and adjust the speed, Option 3 – the savings
inexpensive but extremely would end up over-sized if they and adjusted, which is not speed can be made without and hence the output, of the To give one relatively simple
necessary on close coupled altering pipework, and without pump to suit. example, an 80-25- Starflex belt
pumps. the need for BMS or differential drive pump absorbs 5.77kW at
pressure sensors. Option 2 – savings the projection of the duty point to
Option 1 – installation This option delivers savings of the 1450 rpm curve. An 80-250A
No pipe changes are needed as Option 2 – the solution £3,400 per annum at Armstrong 4280 close coupled
the new rotating assembly fits Replace constant water volume, continuous 50% load. For variable speed IVS Sensorless
into the old pump casing and fixed speed, belt-driven or example, an 80-250 Starflex pump absorbs 1.07kW at 50%
uses the same input/output direct driven pumps on three belt drive pump absorbs load, speed 1010 rpm. A 30%
connections. The close coupled port control, with variable 5.77kW at the projection of the reduction in speed produces a
pump will be approximately speed, variable volume pumps duty point to the 1450 rpm 90% plus reduction in absorbed
150mm longer, so the designer with two port operation. In curve. An 80-250H Starbloc power compared to the original
needs to check that there is addition to giving all the close coupled variable speed belt driven pump. This equates
sufficient space behind the advantages of option one, this IVS Sensorless pump absorbs to annual cost savings of £3750
pump before installation. reduces power consumption at 1.5kW at 50% design flow, at continuous 50% load.
part load, for significantly running at 1000 rpm. A 30% The payback calculator can be
Option 1 – savings reduced running costs. reduction in speed produces an used to analyse figures for other
This is the lowest capital outlay Typically, most heating and energy saving of 74%, pump sizes and before/after
option, but savings would still cooling systems operate at 50% compared with fixed speed. combinations.
be £864 per annum. For design flow. The pump must In summary, the choice of
example, an 80-250 Starflex slow down by about 15% to Option 3 – the outlay and level of work can be
belt drive pump absorbs match its output to this reduced opportunity selected to suit the project
5.77kW at the projection of the demand. Because centrifugal If the budget allows, the budget, but the opportunities for
duty point to the 1450 rpm pumps have a cube law relation greatest potential cost saving cost saving and carbon
curve. An 80-250H Starbloc between speed and absorbed per annum would involve reduction are widespread and
close coupled replacement power, this can reduce power changing out fixed speed, belt- easier to achieve than many
pump absorbs 4.69kW with absorbed by 39%. driven or close coupled pumps might think.
VISIT OUR WEBSITE: www.bsee.co.uk
JUNE 2009 BUILDING SERVICES & ENVIRONMENTAL ENGINEER 17
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